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id=TopBar_bl> <div id=TopBar_right> <a target="_blank" href="http://java.sun.com/javase/6/download.jsp">Download the JDK</a> <br> <a href="../../search.html" target="_blank">Search the Tutorials</a> <br> <a href="javascript:toggleLeft()" id="ToggleLeft">Hide the TOC</a> </div> </div> </div> </div> </div> </div> <div class=PrintHeaders> <b>Trail:</b> Creating a GUI with JFC/Swing <br><b>Lesson:</b> Writing Event Listeners <br><b>Section:</b> Implementing Listeners for Commonly Handled Events </div> <div id=LeftBar class=LeftBar_shown> <div id=Contents> <div class="linkLESSON"><a href="index.html">Writing Event Listeners</a></div><div class="linkAHEAD"><a href="intro.html">Introduction to Event Listeners</a></div><div class="linkAHEAD"><a href="generalrules.html">General Information about Writing Event Listeners</a></div><div class="linkAHEAD"><a href="eventsandcomponents.html">Listeners Supported by Swing Components</a></div><div class="linkAHEAD"><a href="handling.html">Implementing Listeners for Commonly Handled Events</a></div><div class="linkBHEAD"><a href="actionlistener.html">How to Write an Action Listener</a></div><div class="linkBHEAD"><a href="caretlistener.html">How to Write a Caret Listener</a></div><div class="linkBHEAD"><a href="changelistener.html">How to Write a Change Listener</a></div><div class="linkBHEAD"><a href="componentlistener.html">How to Write a Component Listener</a></div><div class="linkBHEAD"><a href="containerlistener.html">How to Write a Container Listener</a></div><div class="linkBHEAD"><a href="documentlistener.html">How to Write a Document Listener</a></div><div class="linkBHEAD"><a href="focuslistener.html">How to Write a Focus Listener</a></div><div class="linkBHEAD"><a href="internalframelistener.html">How to Write an Internal Frame Listener</a></div><div class="linkBHEAD"><a href="itemlistener.html">How to Write an Item Listener</a></div><div class="nolinkBHEAD">How to Write a Key Listener</div><div class="linkBHEAD"><a href="listdatalistener.html">How to Write a List Data Listener</a></div><div class="linkBHEAD"><a href="listselectionlistener.html">How to Write a List Selection Listener</a></div><div class="linkBHEAD"><a href="mouselistener.html">How to Write a Mouse Listener</a></div><div class="linkBHEAD"><a href="mousemotionlistener.html">How to Write a Mouse-Motion Listener</a></div><div class="linkBHEAD"><a href="mousewheellistener.html">How to Write a Mouse-Wheel Listener</a></div><div class="linkBHEAD"><a href="propertychangelistener.html">How to Write a Property Change Listener</a></div><div class="linkBHEAD"><a href="tablemodellistener.html">How to Write a Table Model Listener</a></div><div class="linkBHEAD"><a href="treeexpansionlistener.html">How to Write a Tree Expansion Listener</a></div><div class="linkBHEAD"><a href="treemodellistener.html">How to Write a Tree Model Listener</a></div><div class="linkBHEAD"><a href="treeselectionlistener.html">How to Write a Tree Selection Listener</a></div><div class="linkBHEAD"><a href="treewillexpandlistener.html">How to Write a Tree-Will-Expand Listener</a></div><div class="linkBHEAD"><a href="undoableeditlistener.html">How to Write an Undoable Edit Listener</a></div><div class="linkBHEAD"><a href="windowlistener.html">How to Write Window Listeners</a></div><div class="linkAHEAD"><a href="api.html">Listener API Table</a></div><div class="linkAHEAD"><a href="problems.html">Solving Common Event-Handling Problems</a></div></div> </div> <div id=MainFlow class=MainFlow_indented> <span id=BreadCrumbs> <a href=../../index.html target=_top>Home Page</a> > <a href=../index.html target=_top>Creating a GUI with JFC/Swing</a> > <a href=index.html target=_top>Writing Event Listeners</a> </span> <div class=NavBit> <a target=_top href=itemlistener.html>« Previous</a> • <a target=_top href=../TOC.html>Trail</a> • <a target=_top href=listdatalistener.html>Next »</a> </div> <div id=PageTitle>How to Write a Key Listener</div> <blockquote>Key events tell youwhen the user is typing at the keyboard.Specifically, key events are firedby the component with the keyboard focuswhen the user presses or releases keyboard keys.For detailed information about focus, see <a class="TutorialLink" target="_top" href="../misc/focus.html">How to Use the Focus Subsystem</a>.<blockquote><hr><strong>Note:</strong> For reacting in a special way to particular keys,you usually should use key bindings instead of a key listener.For further information, see <a class="TutorialLink" target="_top" href="../misc/keybinding.html">How to Use Key Bindings</a>.<hr></blockquote><p>You can be notified abouttwo basic kinds of key events:the typing of a Unicode character,and the pressing or releasing of a key on the keyboard.The first kind of event is called a <em>key-typed</em> event.The second kind is either a <em>key-pressed</em> or<em>key-released</em> event.<p>In general, you should try to handle only key-typed eventsunless you need to know when the user presses keysthat don't correspond to characters.For example, if you want to know when the user types someUnicode character — whether as the result of pressingone key such as 'a' or from pressing several keys in sequence —you should handle key-typed events. On the other hand,if you want to know when the user presses the F1 key,or whether the user pressed the '3' key on the number pad,you need to handle key-pressed events.<blockquote><hr><strong>Note:</strong> To fire keyboard events,a component <em>must</em> have the keyboard focus.<hr></blockquote><p>To make a component get the keyboard focus,follow these steps:<ol><li> Make sure the component's <code>isFocusable</code> method returns <code>true</code>. This allows the component to receive the focus. For example, you can enable keyboard focus for a <code>JLabel</code> by calling <code>setFocusable(true)</code> on the label.<li> Make sure the component requests the focus when appropriate. For custom components, you'll probably need to⌨️ 快捷键说明
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